This invention relates to explosive blast suppression, and to an apparatus and method for use therefor.
The use of aqueous foam enclosed in various barrier structures has been employed in the prior art with mixed success. Two related relevant references are, U.S. Pat. Nos. 5,225,622 and 5,394,786. Both references describe a foam-filled enclosure for explosive blast suppression. FIG. 10 of the first patent illustrates a dome-shaped enclosure. It is noted that the diameter of the dome and hence the volume of the enclosure is quite large, i.e. of the order of 12 ft. and is thus inefficient and unnecessarily bulky. Moreover the foam expansion ratio is quite high i.e. 135-1000:1. This causes instability and early breakdown of the foam.
When a blast occurs under aqueous foam, as each bubble bursts, there is an incremental loss of the blast overpressure energy, the net effect of millions of bubbles being destroyed represents a significant blast reduction. Working from the premise that the suppressant quality of the foam would be a function of the mechanical generation and strength of the bubble we have found that superior blast suppression can be achieved by significantly reducing the size of the dome shaped enclosure and the amount of foam material, and by employing a selected aqueous high stability flowable foam material having a low expansion ratio, and low drainage rate properties.
According to one aspect of the invention, an apparatus is provided for suppression of a blast from an explosive device, comprising
a) a hemispherical enclosure defined by an upstanding wall,
b) positioning means associated with the enclosure, for positioning the explosive device within the enclosure substantially equidistant from any point on the wall, and
c) an opening in the wall for receiving an aqueous flowable energy absorbing foam material, having an expansion ratio of 17-49:1, substantially filling said enclosure and covering the device, whereby upon detonation of the explosive device so positioned, the blast is suppressed.
According to another aspect of the invention, a method is provided for suppression of a blast from an explosive device, comprising
a) providing a hemispherical enclosure defined by an upstanding wall,
b) positioning the explosive device within the enclosure, substantially equidistant from any point on the wall, and
c) substantially filling the enclosure and covering the device, with an aqueous energy absorbing flowable foam material having an expansion ratio of 17-49:1, and whereby upon detonation of the device so positioned, the blast is suppressed.